Opponents of fracking will not be credible unless they are prepared to build large-scale renewables projects and damage the environment in the process, Tim Farron has told Politics.co.uk.
The outgoing Liberal Democrat party president, viewed by many as a potential future party leader, has cast further doubt over his party's ongoing commitment to shale gas extraction by repeating his concerns.
"While I accept shale gas has a lesser carbon output than heavy coal, it's still a very large contributor to greenhouse gases," he said.
The Lib Dems adopted to support fracking and nuclear energy in a policy motion at their party's autumn conference in Glasgow.
While Lib Dems in government say the motion is evidence the party is not divided on the issue, Farron said its equivocal nature meant the Lib Dems had only proved they were "agnostic" on the issue.
"My challenge to environmentalists is, how serious are you about climate change?" he added.
"If you really want to do something about it, you need to be prepared to do some things that will have an impact on the environment. If you're going to be against fracking, you've got to be prepared to have tidal schemes built."
Farron's Westmorland and Lonsdale constituency contains the Kent estuary which he believes should be utilised for its energy potential.
He criticised the Environment Agency for blocking small-scale hydroelectric energy schemes but said the main focus should be on larger solutions.
"The potential for renewables is barely being tapped in this country," Farron said. "The focus on small-scale just depresses me.
"You've got an island full of estuaries which we could be tapping, to the tune of gigawatts aplenty."
Projects like the Severn barrage have been blocked by campaigners keen to preserve the estuary's natural beauty, to Farron's frustration.
"The environment lobby have to understand there are no perfect solutions," he said.
"We will have to destroy some ecosystems if we want to build tidal schemes."
Farron spoke out against fracking in August last year, making the first major attack on the process by a senior member of the coalition parties.
But he is not the only Lib Dem concerned about the removal of more fossil fuels from the ground.
A poll by Lib Dem Voice found 46% support fracking, with 36% opposed to it outright.
Former energy and climate change secretary Chris Huhne wrote a devastating critique of the government's approach last month, in which he attacked David Cameron's "fantasy" and warned the prime minister's story about shale gas saving the British economy was "demonstrably and devastatingly false".
Huhne concluded: "To sum up, shale may not happen. If it does, it will be slow. Even if it is eventually massive, prices will not drop. British industry, far from re-shoring, will be squeezed by the strong pound. Could the prime minister please hire a respectable economic adviser with a memory?"